Currently, most powerful rifles in game, not including snipers, are DLT-20a, HB-5 and maybe Valken cause of range. ELG-3A is more powerful and Relby is close to it. And with dual wield those two have even more power. Will it change, or it is planed like that?

ELG can be dual wielded too. And nowhere in world pistols sacrifice range for power. Rifles have both precision and power on there side. So my question still stands, will it be changed or it is done in name of balance, for better gamplay? I dont mind either, just would be nice to know, so we can better organize our weapon acquisition.

Some weapons are better than others. That's intended and it was like that before, as well (though weapons are much more balanced now overall than they were before this update in terms of their overall output across the board). If all were identical there wouldn't need to be any diversity in weapons whatsoever. In this case, of the two dual-wieldable weapons you mention, one is faction restricted and one is publicly available, so this seems okay. Snipers intended to pack the biggest punch, of course.

Specifics subject to change right up until release of full ground combat.